Electro magnetic injector

ABSTRACT

An electromagnetic fuel injector for internal combustion engines wherein the fuel is fed onto the periphery of an annular piston controlled by the armature of the injector electromagnet, so as to enter when the piston is raised an annular chamber communicating with the injection ports in the injector nozzle; said chamber is bounded by the nozzle and the free end of the piston one of the ridges of which cooperates with a seat formed by a frustoconical area on the nozzle, so as to close said chamber when the piston is urged onto its seat by a spring or by a hydraulic reaction.

llnited States Patent 91 Monpetit et al. 1 ay 29, 1973 ELECTRO MAGNETIC INJECTOR [56] References Cited [75] Inventors: Louis A. Monpetit, LEtang La Ville; UNITED STATESPATENTS Herve G Versailles; J- 3,567,135 3/1971 Gebert ..239/533 x Schneider, Mante La Ville; J. W. 2,881,980 4/1959 Beck et al... ....239/585 X Utnalewski, Marly Le Roi, n f 3,288,379 11/1966 Croft et. a1. ....239/533 X France 3,464,627 9/1969 Huber ....239/533 x 3,501,099 3/1970 Benson.... ..239/585 [73] Assignee: Societe 1 Des Procedes Modernes DInjection Sopromi, Les Mureaux, Primary xaminerLloyd L. King France Attorney-Kenyon & Kenyon Reilly Carr & Chapin [21] Appl 135,962 An electromagnetic fuel injector for internal combustion engines wherein the fuel is fed onto the I periphery of an annular piston controlled by the arma- Foreign App Priorlty Data ture of the injector electromagnet, so as to enter when the piston is raised an annular chamber communicat- Apr. 22, 1970 France ..70l45 82 ing with the njection ports in the injec o le; Said chamber is bounded by the nozzle and the free end of [52] US. Cl. ..239/585 the Piston one of the ridges of which cooperates with a [51] Int Cl Bosh 1/30 seat formed by a frustoconical area on the nozzle, so 1 as to close said chamber when the piston is urged onto [58] Field of Search ..239/533, 585

, lts seat by a spring or by a hydraulic reaction.

5 Claims, 4 Drawing Figures @m/ 1 4 m /II 10 /I0 4 9 B 1a ,5" Ba. 12c

zj wz Patented May 29, 1973 3,735,927

2 Sheets-Sheet 1 3 v 83 HT /N VE NTO Q5 (.0 M5 .4. MONPET/ r GUEPET J- S CHNE/DEF? J, M UFNAH. E WSKI ELECTRO MAGNETIC INJECTOR Our invention has for its object improvements in electromagnetic injectors of the type generally provided for apparatus injecting fuel into internal combustion engines.

All such known electromagnetic injectors used for such purposes are generally controlled directly by needle valves. Now, the speed of response in the case of an electromagnet of a predetermined power depends on the cross-sectional area of the port controlled by the needle valve and on the power of the spring urging said needle valve back, since the electromagnet has to overcome, in order to uncover the port, the stresses exerted both by the pressure of the fuel and by the antagonistic spring. In its turn, the power of the electromagnet depends on the one hand on its geometrical size and on the other hand on the width of the gap before operation and, consequently, it is obvious that any limitation applied to the bulk of the injector reduces correspondingly the performances of such injectors, all the more so since the width of the gap depends on the throughput which is to flow through the injector.

As a matter of fact, the difference between the width of the gap before injection and its residuary width upon opening of the injection port corresponds to the path travelled over by the needle valve. Now, the throughput of the injector should depend solely on the actual fuel pressure and not on the cross-sectional area of the passage afforded through the port by the needle valve engaging its conical seat and therefore the stroke executed by the needle valve and, consequently, the width of the gap at the start, should be large enough for the cross-sectional passage released by the needle valve to be much larger than the actual cross-section of the port. Furthermore, if a large throughput is required under a predetermined pressure, the cross-section of the port, thereby also the stroke of the needle valve must be increased. In order to thus increase the stroke of the needle valve, it is necessary to increase the gap whereby the attraction produced by the electromagnet, which is a hyperbolic function of the gap width, decreases and this is in contradistinction with the result sought for, since the increase in the cross-section of the port causes the force required for uncovering the latter to increase, by reason of the hydraulic reaction of the needle valve.

Our invention has for its object to cutout these drawbacks and it covers an electromagnetic fuel-delivering injector, the novelty of which consists in that the closing member is constituted by an annular piston rigid with the movable armature of the electromagnet, said piston sliding fluidtightly with its inner or outer cylindrical surface engaging a guiding member rigid with the injector body; said guiding member is provided with'a frustoconical surface area adapted to engage fluidtightly an annular ridge formed on the sliding piston, so as to define with the latter an annular chamber into which the ducts leading to the injection port or ports open while the space defined within the piston communicates with the inside of the injector body so as to ensure a hydraulic balance which is complete or approximately so.

This arrangement cuts off the hydraulic reaction on the movable section of the injector and it is furthermore possible to limit the stroke of the needle valve to about 0.05 mm. since the cross-sectional area of the passageway defined between the annular ridge and the cooperating fluid-tight surface on the guiding member is always very large as compared with that of the passageway afforded by the actual injection ports, by reason of the comparatively large diameter of the annular piston.

As further developments of this main inventive idea, it is possible:

to provide the stationary section with a central bore inside which is slidingly housed a hollow rod bearing against the movable section which is bored in alignment with the bore in the hollow rod, said hollow rod being urged against said movable section by the end of a spring, the opposite end of which faces an axially bored adjusting screw fitted inside the connection through which the liquid is delivered under pressure;

to provide the annular piston with an inner cylindrical surface adjacent the annular ridge and sliding fluidtightly over the first-mentioned guiding member and with an outer cylindrical surface sliding fluidtightly or substantially so within a second or further guiding member while the inside of the piston communicates with a channel returning the leaks of liquid and the liquid under pressure is delivered into the annular chamber extending between the annular ridge of the piston and the cooperating stationary frustoconical surface the diameters defining the stepped part of the piston being selected in a manner such that a slight hydraulic reaction on the movable section is produced, which reaction urges the piston and movable section onto the seat of the piston, said hydraulic reaction forming a substitute for the return spring to be provided otherwise;

to leave a clearance between the outer cylindrical surface of the piston and the second guiding member so as to allow the liquid to flow inside the injector and thereby cool the latter;

to subject the cooperating surfaces of the stationary and movable sections and the parts of the injector body inside which the latter are carried to a truing operation in a transverse plane while the maximum gap width is defined by a shim fitted between said parts of the injector body inside which the stationary and movable sections are carried;

to resort to stationary and movable sections constituted each by two packs of magnetic lamellations separated by amagnetic shims which latter are provided with central bores, the stationary section and its winding being housed within a corresponding recess formed between two half-shells engaging the opposite sides of the central shim of the movable section and the whole arrangement being carried inside the injector body.

By way of example and in order to further the understanding of our invention, we will now describe three embodiments thereof, reference being made to the accompanying drawings wherein:

FIG. 1 is a diagrammatic sectional view of a first embodiment of our invention.

FIG. 2 is a cross-section through line IIll of FIG. 1.

FIG. 3 is a diagrammatic cross-section of a part of a second embodiment.

FIG. 4 is a diagrammatic cross-section of a part of a third embodiment.

Turning to FIG. 1 or 2, it is apparent that the body of theinjector is constituted by a casing 1 in the upper end of which there is fitted a cover 4 provided with a peripheral fluidtight packing 11, said casing enclosing circuit terminals 9 passing through insulated pinch leads 10 while the liquid is fed under pressure into the casing through the connection 5. The stationary section 17 of the electromagnet is constituted by two packs of magnetic lamellations, separated by a shim of amagnetic material 18 (FlG. 2) and housed within the recesses formed by the half shells 3, the whole arrangement being fitted inside the casing 1. The winding 14 surrounds the central legs of the packs forming the stationary section 17. The latter is held fast within the casing 1 between the cover 4 and a support 2 provided for the nozzle 12, a shim 19 being inserted between said support 2 and the stationary section including the halfshells. Said shim 19 defines the maximum size of gap and the length of travel of the movable section or armature of the electromagnet. The nozzle 12 is provided with injection ports 12a communicating through the oblique ducts 12b with an annular chamber 12c, the entrance of liquid under pressure into which is normally closed by the annular ridge 13a terminating the inner periphery of the annular piston 13, which ridge engages, when at rest, the frustoconical surface 12d along 'the outer periphery of the nozzle 12. The cylindrical outer surface 12g of the nozzle forms a guiding surface for the piston 13 which slides thereon through its inner surface 13d. A fluidtight packing 15 is provided so as to prevent any leaking of liquid under pressure into the annular chamber 120 when the piston 13 rests on its seat at 12d.

The liquid under pressure arriving through the connection 5 at the upper end of the injector body enters the bore 8b inside the hollow tube 8a, beyond which it flows into the axial bore 13f in the piston, which is alined with the bore 8b, and thence through the radial bore 132 into the annular chamber 2a separating the piston 13 from the support 2 carrying the nozzle 12. The piston 13 is urged against its seat at 12d by a spring 7 with the interposition of the tube 8 between the spring and the piston, the outer end of said spring 7 bearing against an axially bored adjusting screw which is not illustrated and is fitted inside the connection 5 with the upper end of the rod 8.

The movable armature of the electromagnet also constituted by two packs of magnetic lamellations is carried within the upper end of the piston 13 and forms with the latter the movable section of the injector.

In order to remove any possible difficulty arising from the allowances in the machining of the various parts, it is of advantage to true the transverse surfaces facing each other on the stationary section of the electromagnet fitted inside the half-shells on the one hand and on the movable armature fitted with the piston 13 inside the nozzle support 2 carrying in its turn the nozzle coaxially with the piston. The width of the gap and consequently the path of the movable section of the armature are defined by the thickness of the shim 19 inserted, when the injector is being assembled, between the half-shells 3 and the nozzle support 2.

The different parts are assembled to form a unit by folding the terminal edges la, 1b of the casing over a flange of the nozzle support 2 and over the cover 4 respectively.

It is apparent from this arrangement that the piston 13 is in perfect hydraulic balance while the stroke of said piston 13 may be very short and of a magnitude of say 0.05mm as provided by the comparatively large diameter of the annular piston and no leaks are possible as long as the piston rests on its seat. The stroke of the piston is measured very accurately by the shim 19 while the allowances in the machining need not be taken into account. The subdivision of the stationary and movable sections 17 and 16 of the actual electromagnet into two halves separated by amagnetic shims furthers also the machining and assembly of the tube 8 and of the part of the piston provided with the axial bore 13f.

FIG. 3 illustrates a modification in the fitting of the piston 13' sliding through its outer surface 13'd inside the cylindrical bore 12'g of the nozzle 12, which latter is fitted directly inside the casing 1 without any intermediate support. The fluidtight packing 15 is fitted in this modified arrangement with the outer surface of the piston 13'. The annular ridge l3'a of the piston engages in this case a frustoconical surface 12'd provided on the inner surface of the nozzle. The annular chamber l2'c between the nozzle and the piston communicates directly with the injection ports 12a in the nozzle. The bores 13'fand l3e are similar to the bores l3fand 13s in FIG. 1 and they play the same parts.

In the embodiment illustrated in FIG. 4, there is provided a connection 5 for the input of liquid under pressure, which connection opens into a duct 511 while a connection returning the leaks is shown at 20. Both connections extend through the cover 4 which carries furthermore the circuit terminals 9 in the pinch leaks 10. A packing 11 is inserted between the cover 4' and the casing wall surrounding the latter. The stationary section of the electromagnet 17 including a winding 14 forms in this embodiment a single part and the same is the case for the movable armature 16'. The stationary section 17 is housed within a recess in the unitary supporting shell 3' and the latter is provided with a first bore 3'a for the entrance of liquid under pressure out of the duct 5a and with a second bore 3'b for the output of leaks towards the connection 20. An intermediate member 23 is fitted between the nozzle support 2 and the supporting shell 3' and is provided with a channel 23a affording a passage for the liquid under pressure while its inner surface 23b forms fluidtight guideway for the outer cylindrical surface 13'c of the piston 13'. The inner cylindrical surface l3'd of the piston slides over the outer cylindrical guiding surface 12'g of the nozzle 12. The annular ridge 13'a of the piston 13' cooperates as in the preceding embodiments with the frustoconical area 12d on the outer surface of the nozzle 12, so as to define therewith an annular chamber communicating under operative conditions with the injection ports 12a through the channels 12b extending across the body of the nozzle 12. The member 16a carrying the movable armature 16' of the electromagnet is rigidly secured to the piston 13 through the expanded head 16b of its lower extension, which head engages the underside of an inner shoulder in the piston. An eccentric bore l3'b in the upper wall of the piston connects the inside of the latter with the bore 3'b through which the leaks of liquid are exhausted. ln order to center the supporting shell 3' with reference to the intermediate member 23, a stud bolt 22 engages simultaneously both parts 3 and 23 and similar centering means, not illustrated, are fitted between the cover 4' and the supporting shell 3'. The width of gap is adjusted, as precedingly, by a shim 19. The different stationary parts are carried inside the casing 1.

it is apparent that the diameter of the upper cylindrical portion 13's of the piston is slightly smaller than that of the annular ridge l3'd whereby the hydraulic reaction is produced by the pressure exerted on the stepped part of the piston facing the bore 23a between the outside of the piston 13 and the inside thereof urges the injector into a closed condition. Consequently, no return spring is required any longer. The ratio between the diameters referred to is selected so as to ensure a speedy closing of the injector after deenergization of the electromagnet 14-17, without it being necessary to overcome an exaggerated closing stress during the openingprocedure.

In order to make some liquid flow permanently through the injector, the cylindrical surface 13c of the piston is fitted in the corresponding bore with a small clearance, which ensures a reduced leak output.

What we claim is:

1. An improved electromagnetic fuel injector for delivering pressured fuel to an internal combustion engine, said fuel injector including an outer casing having a bore therein, a fuel inlet port in said casing in communication with said bore, an annular piston slidably mounted within said bore, an electromagnet having a stationary armature mounted upon said casing and a movable armature coupled to said piston for reciprocating said piston between an opened and closed position, a frustoconical seat disposed adjacent an end portion of said bore, the longitudinal axis of said frustoconical seat being aligned with the longitudinal axis of said bore, a structure forming discharge passage disposed adjacent said seat and extending into communication with the bore, said annular piston having an end portion which is adapted to engage said seat and to prevent flow through said discharge passage, the improvement comprising said annular piston being positioned in said bore by engagement of one of the inner and outer cylindrical surfaces of the annular piston with a mating surface of the bore, the angle formed between the mating surface of the bore and the frustoconical seat being at least greater than 90, said end portion of the annular piston having an annular edge which contacts said seat in the closed position, said annular edge being disposed adjacent the one of the inner and outer cylindrical surfaces of the annular piston which engages the mating surface, said end portion having an end face extending laterally from said annular edge, said end face being in communication with the bore and the fuel inlet port and thereby enabling fuel pressure to be applied to the end face in both the opened and closed positions of the annular piston, in the opened position of the annular piston fuel can flow across the end face and then between the annular edge and the seat in the passage of the fuel from the fuel inlet port to the discharge port, whereby the application of fuel pressure to said end face results in a piston opening force being applied to said annular piston in both the opened and closed positions thereof.

2. An improved electromagnetic fuel injector in accordance with claim 1, and further defined wherein the inner cylindrical surface of the annual piston is engaged with the mating surface of said bore, said annular edge is disposed adjacent the inner cylindrical surface of the annular piston, and said end face extends laterally from said annular edge towards the longitudinal axis of said bore.

3. An improved electromagnetic fuel injector in accordance with claim 2, and further comprising means for placing the inside of said annular piston in communication with said fuel inlet port for preventing hydraulic lock of said annular piston with respect to said mating surface of said bore.

4. An improved electromagnetic fuel injector in accordance with claim 2, and further defined wherein the inner cylindrical surface of the annular piston is slightly spaced apart from said mating surface of said bore for forming a slight clearance therebetween, the slight clearancefor permitting pressured fuel to be leaked into theinside of the annular piston thereby cooling said fuel injector, and further comprising means for exhausting said leaked fuel from the inside of the annular piston and from said fuel injector for preventing hydraulic lock of the annular piston with respect to the mating surface of the bore.

5. An improved electromagnetic fuel injector in accordance with claim 1, and further defined wherein the outer cylindrical surface of the annular piston is engaged with the mating surface of said bore, said annular edge is disposed adjacent the outer cylindrical surface of the annular piston, and said end face extends laterally from said annular edge away from the longitudinal axis of said bore. 

1. An improved electromagnetic fuel injector for delivering pressured fuel to an internal combustion engine, said fuel injector including an outer casing having a bore therein, a fuel inlet port in said casing in communication with said bore, an annular piston slidably mounted within said bore, an electromagnet having a stationary armature mounted upon said casing and a movable armature coupled to said piston for reciprocating said piston between an opened and closed position, a frustoconical seat disposed adjacent an end portion of said bore, the longitudinal axis of said frustoconical seat being aligned with the longitudinal axis of said bore, a structure forming discharge passage disposed adjacent said seat and extending into communication with the bore, said annular piston having an end portion which is adapted to engage said seat and to prevent flow through said discharge passage, the improvement comprising said annular piston being positioned in said bore by engagement of one of the inner and outer cylindrical surfaces of the annular piston with a mating surface of the bore, the angle formed between the mating surface of the bore and the frustoconical seat being at least greater than 90*, said end portion of the annular piston having an annular edge which contacts said seat in the closed position, said annular edge being disposed adjacent the one of the inner and outer cylindrical surfaces of the annular piston which engages the mating surface, said end portion having an end face extending laterally from said annular edge, said end face being in communication with the bore and the fuel inlet port and thereby enabling fuel pressure to be applied to the end face in both the opened and closed positions of the annular piston, in the opened position of the annular piston fuel can flow across the end face and then between the annular edge and the seat in the passage of the fuel from the fuel inlet port to the discharge port, whereby the application of fuel pressure to said end face results in a piston opening force being applied to said annular piston in both the opened and closed positions thereof.
 2. An improved electromagnetic fuel injector in accordance with claim 1, and further defined wherein the inner cylindrical surface of the annual piston is engaged with the mating surface of said bore, said annular edge is disposed adjacent the inner cylindrical surface of the annular piston, and said end face extends laterally from said annular edge towards the longitudinal axis of said bore.
 3. An improved electromagnetic fuel injector in accordance with claim 2, and further comprising means for placing the inside of said annular piston in communication with said fuel inlet port for preventing hydraulic lock of said annular piston with respect to said mating surface of said bore.
 4. An improved electromagnetic fuel injector in accordance with claim 2, and further defined wherein the inner cylindrical surface of the annular piston is slightly spaced apart from said mating surface of said bore for forming a slight clearance therebetween, the slight clearance for permitting pressured fuel to be leaked into the inside of the annular piston thereby cooling said fuel injector, and further comprising means for exhausting said leaked fuel from the inside of the annular piston and from said fuel injector for preventing hydraulic lock of the annular piston with respect to the mating surface of the bore.
 5. An improved electromagnetic fuel injector in accordance with claim 1, and further defined wherein the outer cylindrical surface of thE annular piston is engaged with the mating surface of said bore, said annular edge is disposed adjacent the outer cylindrical surface of the annular piston, and said end face extends laterally from said annular edge away from the longitudinal axis of said bore. 